Lecture 23 Interstellar Chemistry and Life After the Main Sequence

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Lecture 23- Interstellar Chemistry and Life After
the Main Sequence

• Chemistry (defined) as interaction of two (or
  more) molecules to form different molecules

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Interstellar Chemistry
H2, CO, H2O, NH3

• How complicated does it get?

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Our window on interstellar chemistry microwave
spectroscopy

• Each molecule has a unique fingerprint set of
  frequencies

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Example of an interstellar molecule

• Interstellar Acetic Acid, CH3COOH

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Notice other emission lines not identified
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Current State of Astrochemistry

• Table of detected molecules
• gt 110 molecules found in interstellar space
• The largest contain up to 13 atoms
• Many, if not most, are organic
• Nobody doubts there are more complicated species
  lurking out there (unidentified lines)
• Connection to the origin of life?

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Next Topic The Other Side of the Main Sequence.

• All stars in a cluster formed at the same time

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Look at the HR diagram of a cluster

• What can you say?

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Post-Main Sequence Stellar Evolution Example
Betelgeuse

• Lesson 1- Stars get bloated and red

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Post-Main Sequence Stellar Evolution

• The course of evolution depends on mass
• High Mass stellar evolution
• Low Mass stellar evolution
• The two kinds of evolution are quite similar for
  a while, then wildly diverge

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A star at the end of its Main Sequence Lifetime

• No fuel source to keep up the central pressure.
  The core begins to contract under its own gravity

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Contraction continues until proton-proton cycle
begins in shell around the core

• Calculations show that outer layers of star swell
  up to form a red giant